The present invention relates to a display drive control technique for controlling a picture display mode of a display device and particularly to a display drive control circuit for controlling a picture display mode of a display device for displaying still pictures and moving pictures to a liquid crystal display device, an organic EL display device and other dot matrix type display device.
In general, a dot matrix type display device is configured with a display panel including a large number of pixels arranged in a two-dimensional matrix and a display control circuit for displaying still pictures and moving pictures by supplying a picture signal to this display panel. As a display device of this type, a liquid crystal display device, an organic EL display device, a plasma display device or a field emission type display device, etc. are known. Summary of the picture display system is explained here considering, as an example thereof, a liquid crystal display device which is a typical display device and a mobile telephone using the liquid crystal display device as a display section.
Requirement for display of moving pictures on a display screen of a mobile telephone is increasing in recent years. However, since the existing mobile telephone has been mainly used to display still pictures including a text, a drive control circuit thereof is only provided with a still-picture·text·system·I/O·interface and does not comprise an interface corresponding to moving pictures. Accordingly, the existing drive control circuit is capable of displaying moving pictures but it is difficult for such circuit to display moving pictures in higher picture quality which can be seen smoothly.
FIG. 21 is a block diagram for explaining an example of a drive circuit system configuration of a mobile telephone having no interface corresponding to moving pictures which is an example of a display drive control circuit and a display device which have been once discussed by the inventors of the present invention. This display drive control circuit system 1′ is configured with an audio interface (AUI) 2, a high frequency interface (HFI) 3, a picture processor 4′, a liquid crystal controller driver·driver (LCD-CDR) 6′ as a memory 5 and a display drive control circuit and a still-picture·text·system·I/O bus·interface (SS/IF) 7, etc. Reference numeral 9 designates a microphone (M/C); 10, a speaker (S/P); 12, an antenna (ANT); 13, a liquid crystal panel (liquid crystal display; LCD).
The picture processor 4′ is configured with a baseband processor 41 including a digital signal processor (DSP) 411, an ASIC 412 and a microcomputer MPU. The audio interface (AUI) 2 controls prefetch of an audio input from the microphone 9 and output of an audio signal to the speaker 10.
For the display to the liquid crystal panel 13, picture data is read from the memory 5 and is subject to the necessary processes in the microcomputer MPU 413. Thereafter, the picture data is then written into the display RAM within the liquid crystal controller driver (LCD-CDR) 6′. In the moving picture display mode, 10 to 15 frames are changed within a second. In this system, a system I/O bus represented by the 80-system interface is used. The still-picture·text·system·I/O bus·interface (SS/IF) 7 is referred to as system interface 7 in a certain case.
Display operation in the liquid crystal controller driver (LCD-CDR) 6′ is realized with a built-in clock thereof. Therefore, write operation of picture data and display operation thereof are performed asynchronously.